With the emergence of 3 G mobile telephony, new packet-based communication technologies using IP (Internet Protocol) have been developed to support communication involving multimedia services. Furthermore, numerous different mobile and fixed terminals capable of multimedia communication are available on the market. At the same time, a multitude of new services involving communication of various types of media are also constantly being developed to increase the field of usage for various communication terminals. The capacity and capabilities in access and service networks are also ever improved to cater for increased traffic and delivery of more services. For example, one major evolution step for enabling multimedia services has been the introduction of IMS (IP Multimedia Subsystem) which is basically a platform for handling and controlling multimedia sessions.
At present, there is no efficient and consistent way to monitor and assess service quality unambiguously in communication networks. Thus, there is no unified way of monitoring and ensuring that a consumed service actually meets the consumer/user expectations, regardless of what has been guaranteed to the operator. Furthermore, it is also difficult to control whether so-called “Service Level Agreements” (SLAs) are met properly, which can be established between end-users and the networks or between service providers and the networks. For example, if a customer complains that an expected service quality has not been fulfilled during a communication session, the network operator has no means to check the relevance thereof.
In order to evaluate the performance of services in communication networks, one or more known performance indicators can be monitored, often referred to as “Key Performance Indicators”, KPIs. A KPI generally indicates the performance in the network with respect to a predefined factor or parameter more or less relevant for the performance of executed services, service assurance and evaluated SLAs. This factor or parameter can be detected or measured by means of one or more sensors, probes and/or counters in the network to determine an associated current KPI value or level, which typically fluctuates over time.
The KPI values may be derived from information in a session database maintained in a mobile network, but also from other information sources. For example, a predefined KPI may relate to bandwidth occupation, latency, packet loss rate, available bitrate, or network and service accessibility, etc. Thus, a multitude of KPI's related to different aspects of network functions are currently known and can be monitored, using various sensors and counters, in order to evaluate the network and/or service performance.
For example, different network elements in an operator's communication network of today can produce anything from 40 up to 4000 different raw counters or sensors that somehow describe the behaviour of the network. Moreover, in view of the future architecture evolution that can be foreseen today, the number of available counters and sensors in network elements will most likely increase rapidly.
Today, there are a variety of service performance indicators or KPIs in use for performance evaluation, at least in the field of telecommunication. Given the great number of available counters and sensors, the number of available and predefined KPIs will also surely increase rapidly in the future.
However, the immense number of available KPIs presents a great challenge in meeting requirements for user service performance, service assurance and SLAs. Due to the great number of different user services available today, the process of monitoring the performance of all these services can be quite complex. What is more, vendors, operators and service providers rarely choose the same KPIs when evaluating their networks or services, which makes comparisons and reliable assessment the more difficult. For example, the network and its elements might perform well, while the user/consumer experience of a consumed service is still not satisfactory.
As telecommunication services are becoming a significant part of our daily lives, it is important that these services perform to expectations. To achieve and guarantee excellent or at least acceptable service performance can thus be very difficult for network operators using existing quality definitions. So far, network operators have been concerned mainly with the performance of network entities, rather than the performance of the user service itself. “Quality of Service” (QoS) is a technical concept that is often used when evaluating the network and elements therein. However, QoS measurements are typically not suitable to use as a basis for discussing user service performance, since QoS merely provides a description of system capabilities.
In this context, it would be more interesting to gain knowledge of the more user-oriented aspect known as “Quality of Experience” (QoE) which can be very difficult, given the various factors that affect the user's perception of service quality. Among other things, QoE is dependent on purely technical factors such as network coverage and capacity, but also on service offers, support levels, and further subjective factors such as prices and fees. Many of these factors are controlled solely by the network operator or service provider. It is thus highly desirable to provide a consistent and reliable mechanism for enabling evaluation and assessment of user services from a user perspective, i.e. related to QoE.
US 2005/0097209 A1 discloses a solution for measuring “subscriber experience” in a telecommunications network. A management system monitors activity at various interfaces in the communication chain to gather transaction data and to filter this data to provide subscriber-centric QoS metrics in real time. Different probes are used to collect the data from taps at the interfaces and deliver filtered data to a server which determines various KPIs of interest from the delivered data.
WO 2005/032186 A1 discloses how a set of KPIs can be calculated from selected transactions in a traffic database, to characterise the performance of cells in a mobile network in terms of user perceived quality of service parameters.
US 2005/0097209 A1 and WO 2005/032186 A1 represent currently known solutions which focus on determining various KPIs which are generally used to evaluate system-related services in communication networks. However, these solutions are not capable of providing evaluation or assessment of user services that is consistent enough and thereby reliable.